mm: convert deferred_split_huge_page() to deferred_split_folio()

Now that both callers use a folio, pass the folio in and save a call to
compound_head().

Link: https://lkml.kernel.org/r/20230111142915.1001531-28-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/mm/transhuge.rst

@@ -153,8 +153,8 @@ clear where references should go after split: it will stay on the head page.
 Note that split_huge_pmd() doesn't have any limitations on refcounting:
 pmd can be split at any point and never fails.
 
-Partial unmap and deferred_split_huge_page()
-============================================
+Partial unmap and deferred_split_folio()
+========================================
 
 Unmapping part of THP (with munmap() or other way) is not going to free
 memory immediately. Instead, we detect that a subpage of THP is not in use
@@ -166,6 +166,6 @@ the place where we can detect partial unmap. It also might be
 counterproductive since in many cases partial unmap happens during exit(2) if
 a THP crosses a VMA boundary.
 
-The function deferred_split_huge_page() is used to queue a page for splitting.
+The function deferred_split_folio() is used to queue a folio for splitting.
 The splitting itself will happen when we get memory pressure via shrinker
 interface.

include/linux/huge_mm.h

@@ -187,7 +187,7 @@ static inline int split_huge_page(struct page *page)
 {
 	return split_huge_page_to_list(page, NULL);
 }
-void deferred_split_huge_page(struct page *page);
+void deferred_split_folio(struct folio *folio);
 
 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 		unsigned long address, bool freeze, struct folio *folio);
@@ -340,7 +340,7 @@ static inline int split_huge_page(struct page *page)
 {
 	return 0;
 }
-static inline void deferred_split_huge_page(struct page *page) {}
+static inline void deferred_split_folio(struct folio *folio) {}
 #define split_huge_pmd(__vma, __pmd, __address)	\
 	do { } while (0)
 

mm/huge_memory.c

@@ -2815,9 +2815,8 @@ void free_transhuge_page(struct page *page)
 	free_compound_page(page);
 }
 
-void deferred_split_huge_page(struct page *page)
+void deferred_split_folio(struct folio *folio)
 {
-	struct folio *folio = page_folio(page);
 	struct deferred_split *ds_queue = get_deferred_split_queue(folio);
 #ifdef CONFIG_MEMCG
 	struct mem_cgroup *memcg = folio_memcg(folio);

mm/rmap.c

@@ -1427,7 +1427,7 @@ void page_remove_rmap(struct page *page, struct vm_area_struct *vma,
 		 */
 		if (folio_test_pmd_mappable(folio) && folio_test_anon(folio))
 			if (!compound || nr < nr_pmdmapped)
-				deferred_split_huge_page(&folio->page);
+				deferred_split_folio(folio);
 	}
 
 	/*